Cellulose triacetate film is transparent, has excellent physical and mechanical qualities, and exhibits minimal dimensional variation due to variation of temperature as well as humidity. Heretofore, it has been widely employed as a base for photographic film, drawing tracing film, electrical insulating materials and the like, and recently, has been employed as a protective film for a polarizing plate of liquid crystal displays or a support for optical compensating films. The cellulose triacetate film employed for the protective film for the polarizing plate of a liquid crystal display element is required to exhibit high light transmission, non-optical orientation, excellent adhesion to polarizing film, excellent flatness, high absorption of ultraviolet radiation, and the like. Further, when employed as the liquid crystal display installed in cars, demanded is excellent durability such as no degradation at high humidity as well as high temperature, excellent dimensional stability, and the like.
The aforementioned cellulose triacetate film exhibits excellent quality such as light transmission, non-optical orientation, and the like. However, since it does not absorb ultraviolet radiation, in order to minimize the degradation of the liquid crystal display due to ultraviolet radiation, UV absorbers are commonly incorporated into the cellulose triacetate film employed as a protective film for the polarizing plate, which is provided on the outermost surface of the liquid crystal display.
In more detail, in the cellulose ester film employed as the protective film for the liquid crystal, fine particles are incorporated to improve ultraviolet radiation resistance as well as conveyance properties. For instance, Japanese Patent Publication Open to Public Inspection No. 6-130226 describes a technique regarding incorporation of metal oxide particles having a diameter of not more than 0.2 μm; Japanese Patent Publication Open to Public Inspection No. 10-44327 describes a technique in which particles are applied onto cellulose ester film; and Japanese Patent Publication Open to Public Inspection No. 10-95862 describes a technique in which particles are incorporated and the transparency of the resulting cellulose ester is not degraded. In all of these, film is produced by casting dissolved cellulose ester.